This invention relates to meltblown webs and in particular to meltblown webs having meltblown fibers and particles.
It has been desired to provide particle-containing meltblown webs for a variety of purposes, wherein a predetermined amount of particles is held in the web while minimizing the amount of xe2x80x9cdustingxe2x80x9d (i.e., particles undesirably dropping out of the web) the web may suffer.
Various approaches to retaining particles within a web have been proposed. One such approach discloses a self-supporting durable flexible conformable low-pressure-drop porous sheet product that contains a uniform three-dimensional arrangement of discrete particles. The sheet product includes, in addition to the particles, a web of meltblown fibers in which the particles are uniformly dispersed. The particles are physically held, such as by mechanical entanglement, in the web even though there is only point contact between the meltblown fibers and the particles. (xe2x80x9cPoint contactxe2x80x9d occurs when preformed bodies abut one another. It is distinguished from xe2x80x9carea contact,xe2x80x9d such as results when a liquid material is deposited against a substrate, flows over the substrate, and then hardens in place.) Even though the particles are mechanically entangled within the interstices of the web, a portion of the particles still undesirably drop out of the web during handling.
Another approach discloses using adhesive polymers for forming the meltblown web. In addition to being physically entrapped in the web, the particles of this approach are also adhered to the surfaces of the meltblown fibers. Even though this may be viewed as an improvement over retaining particles within a web by point contact, this approach accomplishes its objective with the use of expensive adhesive polymers.
For the foregoing reasons, there is a need for improved meltblown webs having particles substantially uniformly and homogeneously dispersed therethrough and retained therein by more than mere point contact or mechanical entanglement, wherein dusting is substantially eliminated.
The present invention is directed to improved meltblown webs having particles substantially uniformly and homogeneously dispersed therethrough and that satisfies the need to substantially eliminate dusting.
In one embodiment of the present invention, a substantially nondusting meltblown web includes at least one air-formed nonparticle-containing layer having meltblown fibers and staple fibers. The staple fibers engage at least some of the meltblown fibers to space the meltblown fibers apart from each other. Also, the staple fibers are retained within the nonparticle-containing layer by entanglement with the meltblown fibers. In addition to including at least one air-formed nonparticle-containing layer, this embodiment of the substantially nondusting web includes at least one air-formed particle-containing layer having meltblown fibers, particles and staple fibers. The particles are retained in the particle-containing layer by surface penetration into the meltblown fibers. Similar to the nonparticle-containing layer, the staple fibers of the particle-containing layer engage at least some of the meltblown fibers to space the meltblown fibers apart from each other. Also, the staple fibers are retained within the particle-containing layer by entanglement with the meltblown fibers.
In an alternative embodiment of the present invention, a substantially nondusting meltblown web includes at least one air-formed layer having meltblown fibers and particles. The particles are retained within the layer by surface penetration into the meltblown fibers.
In yet another embodiment of the present invention, a substantially nondusting meltblown web includes at least one layer having meltblown fibers, particles and staple fibers. The particles are retained within the layer by surface penetration into the meltblown fibers. The staple fibers engage at least some of the meltblown fibers to space the meltblown fibers apart from each other. Also, the staple fibers are retained within the layer by entanglement with the meltblown fibers.